Circuit breakers are used to switch large currents, typically currents of more than 100 A. Typically a circuit breaker consists of a casing and switching poles fitted therein. The electrical opening and closing of the circuit is effected in the switching poles.
To simplify assembly of the switching poles use is made of a “casing”. Typically this casing consists of a bottom section, a top section and a top cover. The switching poles are mounted in the bottom section, with the top section or top cover mounted above serving as cover and protection.
Above nominal currents of 250 A busbars are preferably used to carry the current rather than cable connections. These busbars are typically made of copper or aluminum. To mount a circuit breaker in an electrical installation the premounted, rigid busbars are first swung away, and then the circuit breaker is mounted in the bottom section of the casing and likewise premounted in the electrical installation. Finally the busbars are swung in and connected to the electrical contacts of the switching poles.
The premounted rigid busbars approximately describe a circular path when being swung away from or into the circuit breaker. The casing of the circuit breaker should be designed such that the busbars can be swung in to the contacts of the switching poles, if busbar and bottom section are for example premounted in a switching cabinet. After being swung in, the busbar is connected to the electrical contact of the switching pole, e.g. via a screw connection.
Until now the problem of being able to swing the rigid premounted busbars in has been solved by an array-like structure in the bottom section of the casing of the circuit breaker according to FIG. 4. For the chamber of an individual switching pole this means that in accordance with FIG. 4 the bottom section consists of a base area and two rectangular side faces running parallel to one another and connected to the base area. Typically casings are manufactured as cast housings made of a thermoplastic. The array-like structure in accordance with FIG. 4 proves to be of little advantage here because of the significant tendency of the bottom sections manufactured using a casting process to warp and collapse. This warping of the bottom section is shown in FIG. 5 on the basis of two bottom sections of a casing: the bottom section shown by dashed lines and the bottom section shown by unbroken lines show the strong geometric deviation of the injection-molded component from the desired shape.